Recording liquid, liquid cartridge, liquid discharge apparatus and method of liquid discharge

ABSTRACT

According to the present invention, an ink ( 2 ) containing an EO adduct of a dihydric alcohol, having a hydrocarbon group with 9 or less carbon atoms and having an I/O ratio ranging between 1 and 1.37, is supplied via nozzles ( 42   a ) in the form of liquid droplets i onto a recording paper sheet P, so that fine bubbles may be suppressed from being generated in the ink ( 2 ) to prevent emission defects such as non-emission or warped emission, and hence a high quality image free of blurring or white spots may be produced.

TECHNICAL FIELD

This invention relates to a recording liquid deposited on a support inthe state of droplets for recording thereon, a liquid cartridge forholding the recording liquid, and to a liquid emitting device and aliquid emitting method for emitting the recording liquid, contained inthe liquid cartridge, as droplets through an emitting opening onto thesupport.

This application claims priority of Japanese Patent Application No.2003-360027, filed in Japan on Oct. 20, 2003, the entirety of which isincorporated by reference herein.

BACKGROUND ART

As a liquid emitting device, there is an ink jet printer apparatus inwhich a recording liquid, or a so-called ink, is emitted via an inkemitting head to a recording paper sheet, as a support, to record animage or a letter/character thereon. The printer apparatus of the inkjet system has advantages such as low running costs, small size, andease in printing a colored image.

The ink jet system, emitting the ink via an ink emitting head, may beimplemented by, for example, a deflection system, a cavity system, athermo-jet system, a bubble-jet system (registered trademark), thermalink jet system, a slit jet system, or a spark jet system. Based on thesevarious operating principles, the ink is turned into fine liquiddroplets, which are then emitted via emitting openings, that is,nozzles, of an ink emitting head, so as to be deposited on the sheet forrecording an image or a letter/character thereon.

Meanwhile, a demand is raised for the nozzles not to be stopped up withthe recorded liquid used in the ink jet recording system. It has so farbeen felt that fine bubbles in the ink represent one of the factorspossibly responsible for nozzle clogging.

In the ink, a preset quantity of a gas, such as air, remains dissolved.If, with rise in temperature, the gas is lowered in solubility, the gaswhich may not be dissolved in the liquid is separated to form finebubbles in the liquid. Specifically, when the ink present in an ink tankadapted for supplying the ink to e.g. an ink emitting head, in an inkduct or in an ink emitting duct rises in temperature, the gas dissolvedin the liquid is released to form fine bubbles.

When these fine bubbles are present in the ink emitting head, emissiontroubles, such as non-emission of the ink from the nozzle or warpedemission of the ink, that is, the ink being emitted from the nozzlealong a path offset from the intended path, are produced, with theresult that printed image suffers from white spots or becomes blurred todegrade the printing quality.

In the recording system in which the ink is turned into fine liquiddroplets, under the action of thermal energy, and the so formed liquiddroplets are emitted from the nozzle, that is, in the recording systemof the thermal type or the bubble jet type, the ink is heated rapidly bya heater and emitted in the form of liquid droplets under the pressureof air bubbles generated by film boiling of the ink. Thus, heat isaccumulated in the vicinity of the heater, and hence the ink in the inkduct is extremely liable to be raised in temperature, with the resultthat emission troubles, such as the aforementioned non-emission orwarped emission, tend to be produced to a pronounced extent.

For combating such problem, it is proposed in e.g. the JP PatentPublications 1 and 2 to use an aqueous pigment ink doped with apropylene oxide adduct polymer of lower alcohol. However, theseproposals are not up to sufficient suppression of fine bubbles andfurther improvement has been desired.

It has also been proposed in Patent Publication 3 to add an ethyleneoxide adduct of a higher dehydrate alcohol alkoxylate in an aqueouspigment ink. The ink proposed in this Patent Publication 3 is alleged tobe superior in emission stability during high frequency driving,penetrability to the recording paper sheet and in drying properties.However, if a compound obtained on adding only ethylene oxide to thehigher alcohol a dihydric alcohol alkoxylate is contained in the ink, inassociation with the teaching by Patent Publication 1, it has not beenpossible to cope successfully with the problem of the nozzles beingstopped with fine bubbles. Specifically, the ink obtained on adding 7mol or more only of ethylene oxide undergoes vigorous foaming to causesevere nozzle clogging.

On the other hand, with the ink used for the ink jet recording system, ademand has been raised not only for prohibiting nozzle clogging but alsofor preventing the optical density from being lowered or for preventingthe boundary bleeding or speckled color mixing in all-over printing,even in case of printing on a medium grade paper sheet, such as copypaper sheet or report paper sheet, or a high grade paper sheet.

For meeting the demand, it has been proposed in e.g. Patent Publication4 to use a compound, obtained on treating a water-insoluble colorantwith a high polymer material containing a sulfonic acid (sulfonate)group and/or with a high polymer material containing phosphoric acid(phosphate) group, as a colorant, and also to add a high polymermaterial, including a carboxylic acid (carboxylate) to the ink. It hasalso been proposed in Patent Publication 5 to get the ink doped with analginic acid having a D-mannuronic acid to L-guluronic acid ratioranging between 0.5 and 1.2. It has also been proposed in PatentPublication 6 to add at least one surfactant selected from the group offluorine-based surfactants and silicon-based surfactants and alginatesto the ink. However, neither of these Publications is sufficient to meetthe aforementioned demand and further improvement has been desired.

On the other hand, the aforementioned problem, related with the bubbles,occurs more pronouncedly with a printer apparatus capable of performinghigh-speed printing on a recording paper sheet, that is, a line-basedprinter apparatus having an ink emitting range substantially equal tothe width of the recording paper sheet (for example, see PatentPublications 7 to 9).

More specifically, with a line-based printer apparatus, having one ormore rows of nozzles juxtaposed in a direction substantially at rightangles to the width-wise direction of the recording paper sheet, asdistinct from a serial-based printer apparatus in which an ink emittinghead is scanned in a direction substantially at right angles to the feeddirection of the recording paper sheet, an ink duct for conducting theink from an ink tank is formed for traversing the feed direction of therecording paper sheet, and in which a plural number of ink emittingheads, each having a nozzle, are arrayed on one or both sides of the inkduct, the number of ink heating sites is correspondingly increased withthe number of the nozzles, so that fine bubbles tend to be generated.Moreover, the ink tank is separated from the ink emitting head a longdistance, whilst the structure from the ink tank to the ink emittinghead is complicated to render it difficult to remove the fine bubblesgenerated, with the result that inconveniences ascribable to the finebubbles occur most pronouncedly.

With the line-based printer apparatus, the period of emission of liquiddroplets from one nozzle line to the next is that short and hence an inkexhibiting superior penetration characteristics into the recording papersheet needs to be used. If the ink of this sort is used for a papersheet of medium quality, the ink exhibits the tendency to seep into thepaper sheet along its depth, that is, along its thickness, with theresult that the optical density tends to be lowered.

In addition, if so-called color printing of emitting inks of differentcolors on a recording paper sheet, is to be carried out with theline-based printer apparatus, where the period of emission of liquiddroplets from one nozzle line to the next is short, a color liquiddroplet is deposited before the previously deposited color liquiddroplet sufficiently seeps into the bulk part of the paper sheet, withthe consequence that boundary bleeding or speckled color mixing inall-over printing tends to be produced between different colors.

-   Patent Publication 1: Japanese Laid-Open Patent publication    2001-2964-   Patent Publication 2: Japanese Laid-Open Patent publication    H10-46075-   Patent Publication 3: Japanese Laid-Open Patent publication H7-70491-   Patent Publication 4: Japanese Laid-Open Patent publication    2000-154342-   Patent Publication 5: Japanese Laid-Open Patent publication    H8-290656-   Patent Publication 6: Japanese Laid-Open Patent publication    H8-193177-   Patent Publication 7: Japanese Laid-Open Patent publication    2002-36522-   Patent Publication 8: Japanese Laid-Open Patent publication    2001-315385-   Patent Publication 9: Japanese Laid-Open Patent publication    2001-301199

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a recording liquidwhereby the aforementioned problems of the related art may be overcome.

It is another object of the present invention to provide a recordingliquid suffering from foaming only to a lesser extent, superior inemission stability, exhibiting high optical density in case ofmulti-color printing of an image or a letter/character on a paper sheetof a medium quality, as a support, and which is free from boundarybleeding or speckled color mixing in all-over printing to lend itself tohigh-quality printing, a liquid cartridge containing the recordingliquid, and a method and a device capable of effecting high qualityprinting using the recording liquid contained in the liquid cartridge.

The present invention provides a recording liquid deposited on a supportin the state of liquid droplets for recording thereon, comprising adyestuff, a solvent for dispersing the dyestuff, and an ethylene oxideadduct of a a dihydric alcohol, containing a hydrocarbon group with 9 orless carbon atoms and having a ratio I/V of an inorganic value (IO) toan organic value (OV) not less than 1 and not larger than 1.37.

The present invention also provides a liquid cartridge mounted to aliquid supply device for operating as a supply source for the recordingliquid for the liquid supply device, the liquid supply device beingprovided to a liquid emitting device adapted for emitting the recordingliquid, held in a liquid vessel, in the form of liquid droplets, anddepositing the emitted ink on a support, for effecting the recording.The recording liquid comprises a dyestuff, a solvent for dispersing thedyestuff and an ethylene oxide adduct of a dihydric alcohol, containinga hydrocarbon group with 9 or less carbon atoms and having a ratio I/Vof an inorganic value (IO) to an organic value (OV) not less than 1 andnot larger than 1.37.

The present invention also provides a liquid emitting device comprisingemitting means including a liquid chamber for storing a recordingliquid, a supply part for supplying the recording liquid to the liquidchamber, one or more pressure generating element(s) provided to theliquid chamber for thrusting the recording liquid stored in the liquidchamber, and an emitting opening for emitting the recording liquid,thrust by the pressure generating element, onto the major surface of asupport from the liquid chamber as liquid droplets, and a liquidcartridge connected to the emitting means for operating as a supplysource for the recording liquid. The recording liquid comprises adyestuff, a solvent for dispersing the dyestuff and an ethylene oxideadduct of a dihydric alcohol, containing a hydrocarbon group with 9 orless carbon atoms and having a ratio I/V of an inorganic value (IO) toan organic value (OV) not less than 1 and not larger than 1.37.

The present invention also provides a liquid emitting method employing aliquid emitting device comprising emitting means including a liquidchamber for storing the recording liquid, a supply part for supplyingthe recording liquid to the liquid chamber, one or more pressuregenerating element(s) provided to the liquid chamber for thrusting therecording liquid stored in the liquid chamber, and an emitting openingfor emitting the recording liquid, thrust by the pressure generatingelement, onto the major surface of a support from the liquid chamber asliquid droplets, and a liquid cartridge connected to the emitting meansfor operating as a supply source for the recording liquid. The recordingliquid comprises a dyestuff, a solvent for dispersing the dyestuff andan ethylene oxide adduct of a dihydric alcohol, containing a hydrocarbongroup with 9 or less carbon atoms and having a ratio I/V of an inorganicvalue (IO) to an organic value (OV) not less than 1 and not larger than1.37.

Thus, according to the present invention, in which the recording liquidcontains an ethylene oxide adduct of a dihydric alcohol, having ahydrocarbon group with 9 or less carbon atoms and having a ratio I/V ofan inorganic value (IO) to an organic value (OV) not less than 1 and notlarger than 1.37, it becomes possible to prevent fine bubbles from beinggenerated in the recording liquid, while it also becomes possible toprevent emission defects, such as non-emission or warped emission of therecording liquid from the emitting openings. The result is that,according to the present invention, the emission defects ascribable tofine bubbles generated in the recording liquid may be prevented toeliminate blurring or generation of white spots, and that, since therecording liquid may exhibit superior wettability for the support, it ispossible to achieve high quality recording of high optical density freeof boundary bleeding or speckled color mixing in all-over printing.

Other objects and specified advantages of the present invention willbecome more apparent from the following explanation of preferredembodiments thereof especially when read in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a printer apparatus embodying thepresent invention.

FIG. 2 is a perspective view showing a head cartridge provided to theprinter apparatus.

FIG. 3 is a cross-sectional view showing the head cartridge.

FIGS. 4A and 4B show an ink supply part when an ink tank is fitted tothe head cartridge, where FIG. 4A is a schematic view showing the closedstate of the ink supply part and FIG. 4B is a schematic view showing theopened state of the ink supply part.

FIG. 5 is a schematic view showing the relationship between the ink tankand an ink emitting head in the head cartridge.

FIGS. 6A and 6B show a valving mechanism in a connecting part of the inktank, where FIG. 6A is a cross-sectional view with a valve in the closedstate and FIG. 6B is a cross-sectional view with the valve in the openedstate.

FIG. 7 is a cross-sectional view showing the structure of the inkemitting head.

FIGS. 8A and 8B show the ink emitting head, where FIG. 8A is a schematiccross-sectional view showing the state in which an air bubble has beenformed on a heater resistor and FIG. 8B is a schematic cross-sectionalview showing the state in which the ink liquid droplet has beendischarged from the nozzle.

FIG. 9 is a partial see-through side view of the printer apparatus.

FIG. 10 is a schematic block diagram showing a control circuit of theprinter apparatus.

FIG. 11 is a flowchart showing the printing operation of the printerapparatus.

FIG. 12 is a partial see-through side view of the printer apparatus,shown with a head cap opened.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the drawings, a recording liquid, a liquid cartridge, aliquid emitting device and a liquid emitting method, embodying thepresent invention, will be explained in detail. An ink jet printerapparatus, referred to below as a printer apparatus 1, shown in FIG. 1,emits e.g. the ink to a recording paper sheet P, running in a presetdirection, for printing an image or a letter/character thereon. Also,the printer apparatus 1 is a so-called line-based printer including aplural number of ink emitting openings (nozzles) juxtaposedsubstantially in a line along the width of the recording paper sheet P,that is, in a direction indicated by arrow W in FIG. 1, in keeping withthe printing width on the recording paper sheet P.

Referring to FIGS. 2 and 3, this printer apparatus 1 includes an ink jetprinter head cartridge, referred to below as a head cartridge 3, foremitting an ink 2, as a recording liquid for recording an image or aletter/character on the recording paper sheet P, and a main printer bodyunit 4 for loading the head cartridge 3 thereon. In the present printerapparatus 1, the head cartridge 3 may be mounted on or dismounted fromthe main printer body unit 4, whilst ink tanks 11 y, 11 m, 11 c and 11 kmay be mounted on or dismounted from the head cartridge 3. These inktanks are liquid cartridges containing the ink 2, and operate as inksupply sources for the head cartridge 3. With the printer apparatus 1,the ink tank 11 y for yellow, the ink tank 11 m for magenta, the inktank 11 c for cyan and the ink tank 11 k for black, are usable. The headcartridge 3, that may be mounted on or dismounted from the main printerbody unit 4, and the ink tanks 11 y, 11 m, 11 c and 11 k, that may bemounted on or dismounted from the head cartridge 3, are consumableitems.

With the printer apparatus 1, the recording paper sheet P, housed in atray 55 a, adapted for accommodating a stack of the plural recordingpaper sheets P therein, may be mounted in a tray loading unit 5,provided on the front bottom part of the main printer body unit 4, forsupplying the recording paper sheets P into the inside of the mainprinter body unit 4. When the tray 55 a is loaded on the tray loadingunit 5 on the front surface of the main printer body unit 4, therecording paper sheet P is supplied by a paper sheetsupplying/discharging mechanism 54 via paper sheet supply port 55 to theback surface side of the main printer body unit 4. The recording papersheet P, forwarded to the back surface side of the main printer bodyunit 4, has its running direction reversed by a reversing roll 83, aslater explained, and is forwarded on the upper forward running path fromthe back surface side towards the front side of the main printer bodyunit 4. Before the recording paper sheet P, forwarded from the backsurface side of the main printer body unit 4 towards its front surface,is discharged from a discharge opening 56 provided in the front surfaceof the main printer body unit 4, printing data, corresponding to inputletter/character data, entered from an information processing apparatus69, such as a personal computer, which will be explained subsequently,is printed as letter/character on the so forwarded recording paper sheetP.

The ink 2, used as a recording liquid in printing, contains a colorantmaterial, such as various pigments or water-soluble dyes, acting asdyestuff, a solvent for dispersing the colorant material, and anethylene oxide (EO) adduct of a dihydric alcohol with a ratio of aninorganic value (IO) to an organic valur (OV), referred to below as I/Oratio, ranging between 1 and 1.37.

As the colorant material, fine particles of dyes, pigments or coloredpolymers, well-known in the art, may be used alone or as a mixture. Inparticular, the water-soluble dyes are preferred. As the water-solubledyes, any of acidic dyes, direct dyes, basic dyes, reactive dyes oredible dyes may be selected and used, mainly from the perspective ofsolubility in water, coloration and color fastness.

Specifically, the yellow water-soluble dyes may be enumerated by, forexample, C.I. Acid Yellow 17, 23, 42, 44, 79 and 142, C.I. Food Yellow 3and 4, C.I. Direct Yellow 1, 12, 24, 26, 33, 44, 50, 86, 120, 132, 142and 144, C.I. Direct Orange 26, 29, 62 and 102, C.I. Basic yellow 1, 2,11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 40, 41, 45, 49, 51,53, 63, 64, 65, 67, 70, 73, 77, 87 and 91, C.I. Reactive Yellow 1, 5,11, 13, 14, 20, 21, 22, 25, 40, 47, 51, 55, 65 and 67.

The magenta water-soluble dyes may be enumerated by, for example, C.I.Acid Red 1, 8, 13, 14, 18, 26, 27, 35, 37, 42, 52, 82, 87, 89, 92, 97,106, 111, 114, 115, 134, 186, 249, 254 and 289, C.I. Food Red, 7, 9 and14, C.I. Direct Red 1, 4, 9, 13, 17, 20, 28, 31, 39, 80, 81, 83, 89, 225and 227, C.I. Basic Red 2, 12, 13, 14, 15, 18, 22, 23, 24, 27, 29, 35,36, 38, 39, 46, 49, 51, 52, 54, 59, 68, 69, 70, 73, 78, 82, 102, 104,109 and 112, and C.I. Reactive Red 1, 14, 17, 25, 26, 32, 37, 44, 46,55, 60, 66, 74, 79, 96 and 97.

The cyan water-soluble dyes may be enumerated by, for example, C.I. Acidblue 9, 29, 45, 92 and 249, C.I, Direct Blue 1, 2, 6, 15, 22, 25, 71,76, 79, 86, 87, 90, 98, 163, 165, 199 and 202, C.I. Basic Blue 1, 3, 5,7, 9, 21, 22, 26, 35, 41, 45, 47, 54, 62, 65, 66, 67, 69, 75, 77, 78,89, 92, 93, 105, 117, 120, 122, 124, 129, 137, 141, 147 and 155, andC.I. Reactive Blue 1, 2, 7, 14, 15, 23, 32, 35, 38, 41, 63, 80 and 95.

The black water-soluble dyes may be enumerated by, for example, C.I.Acid Black 1, 2, 7, 24, 26 and 94, C.I. Food Black 1 and 2, C.I. DirectBlack 19, 22, 32, 38, 51, 56, 71, 74, 75, 77, 154, 168 and 171, and C.I.Basic Black 3, 4, 7, 11, 12 and 17.

The amount of addition of the aforementioned colorant to the ink 2ranges between 1 mass wt % to 10 mass wt %, preferably between 3 mass wt% and 5 mass wt %, to the total mass weight of the ink 2, and isdetermined in consideration of, for example, the viscosity, dryingperformance, emitting stability of coloration properties of the ink andpreservation stability of the printed product.

Although the ink 2 is used dissolved in water, as a solvent, it is alsopossible to use well-known organic solvents, either singly or incombination, for the purpose of imparting desirable physical propertiesto the ink 2, improving dispersibility and solubility in water of thecolorant and preventing the ink 2 from drying.

More specifically, the organic solvents, usable as solvents, may beenumerated by, for example, lower alcohols, such as ethanol, 2-propanol,polyhydric alcohols, such as ethylene glycol, diethylene glycol,triethylene glycol, polyethylene glycol, polypropylene glycol,1,5-pentanediol, 1,6-hexanediol, glycerin, 1,2,6-hexanetriol,1,2,4-butanetriol or petriol, polyhydric alcohol alkylethers, such asethyleneglycol monoethylether, ethyleneglycol monobuthylether,diethyleneglycol monomethylether, diethyleneglycol monoethylether,diethyleneglycol monobuthylether, tetraethyleneglycol monomethylether,or propyleneglycol monophenylether, polyhydric alcohol allylethers, suchas ethyleneglycol monophenylether or ethyleneglycol monobenzylether,nitrogen-containing heterocyclic compounds, such asN-methyl-2-pyrrolidone, N-hydroxyethyl-pyrrolidone,1,3-dimethylimidazoline,

-caprolactam or

-butyrolactone, amides, such as formamide, N-methyl formamide,N,N-dimethylformamide, aimes, such as monoethanolamine, diethanolamine,triethanolamine, monoethylamine, diethylamine or triethylamine, andsulfur-containing compounds, such as dimethyl sulfoxide, sulfolane orthiodiethanol.

The amount of addition of the aforementioned organic solvents in the ink2 ranges between 5 mass wt % to 50 mass wt %, preferably between 10 masswt % and 35 mass wt %, based on the total mass weight of the ink 2, andis determined in consideration of the viscosity, drying performance oremission stability of the ink 2, as in the case of the colorant.

Examples of the EO adduct of the a dihydric alcohol, with a hydrocarbongroup with the number of carbon atoms not larger than 9, and with therange of the I/O ratio between 1 and 37, include organic compounds shownby the chemical formulas 4 to 8, which may be used either singly or incombination:

Although the reason is not clear, with the ink 2 containing theaforementioned EO adducts of the a dihydric alcohols, described above,fine bubbles may be suppressed from being generated to prevent a nozzles42 a as later explained from being stopped with the fine bubbles, withthe result that failure in ink emission such as the ink not beingemitted from the nozzles 42 a or the ink being emitted in a directionoffset from the intended direction to cause emission deviation, may beprohibited to achieve superior emission stability. Moreover, althoughthe reason is again not clear, in the ink 2, containing the EO adduct ofa dihydric alcohol, described above, the optical density of an imageobtained on recording by deposition thereof on the recording paper sheetP, that is, on printing, becomes higher to suppress boundary bleeding orspeckled color mixing in allover printing to achieve an image printed tohigh quality.

Moreover, with the ink 2, containing, as the EO adduct of a dihydricalcohol with the number of carbon atoms not larger than 9 and with theI/O ratio ranging between 1 and 1.37, the EO adduct of the dihydricalcohol, with hydrocarbon groups with an iso-branching or atert-branching, as indicated by the chemical formulas 9 to 16, the inkmay further be improved in emission stability, so that a printed imageobtained may be of higher quality, because the steric chemical structureof the EO adduct of the a dihydric alcohol is further deterrent to thegeneration of fine bubbles. In particular, as the ink 2, the compoundsindicated by the chemical formulas 11 to 16 are preferably contained asthe EO adduct of a dihydric alcohol with the number of carbon atoms notlarger than 9 and with the I/O ratio ranging between 1 and 1.37. Withthe ink containing these compounds either alone or in combination,outstanding operation and effects may be produced.

If, with the EO adduct of the dihydric alcohol, contained in the ink 2,the number of carbon atoms exceeds 9, the ink 2 is increased inviscosity and, depending on the content of the organic compound, the ink2 tends to be deteriorated in penetrability into the recording papersheet P. Meanwhile, in the EO adduct of the dihydric alcohol, the numberof carbon atoms is spontaneously determined by the value of the I/Oratio.

The EO adduct of a dihydric alcohol, with the number of carbon atoms notlarger than 9 and with the I/O ratio ranging between 1 and 1.37, ispreferably contained in an amount ranging between 0.1 mass wt % and 5mass wt %, more preferably, in an amount ranging between 0.5 mass wt %and 3 mass wt %, based on the total mass weight of the ink 2. If theamount of content of the EO adduct of a dihydric alcohol is smaller than0.1 mass wt %, it becomes difficult to achieve the aforementionedfavorable operation and results. If conversely the amount of content ofthe EO adduct of a dihydric alcohol is larger than 5 mass wt %, the ink2 tends to be higher in viscosity and deteriorated in penetrability intothe recording paper sheet P.

This EO adduct of a dihydric alcohol has the ratio of the inorganicvalue (IV) to the organic value (OV) not less than 1 and not larger than1.37, as described above. These inorganic value (IV) and organic value(OV) may be found from discussions on an organic conceptual diagramshown e.g. in Yoshio Koda: “Systematic Organic QualitativeAnalysis-Fundamentals and Application”, published by SANKYO PublishingCo. Ltd., 1984, Fujita and Akatsuka, “Systematic Organic QualitativeAnalysis (for Mixtures)”, published by Kazama-Shobou (1974), NonuhikoKuroki, “Theoretical Chemistry on Dyes”, published by Maki-Shoten, 1966,Tobita and Uchida, “Fine Chemicals”, Maruzen (1982) and in Inoue, Ueharaand Minami, “Method for Separating Organic Compounds”, published byShoukabou, 1990. The discussions on an organic conceptual diagram arerelative with a technique of grasping the physical properties of asubject organic compound by combining ‘inorganic properties’, denotingthe degree of the physical and chemical properties of an organiccompound by the force of electrical affinity, and ‘organic properties’,denoting the degree of the physical and chemical properties of theorganic compound by the Van Der Waals force.

That is, with the I/O, if the inorganic value (IV) of a given compoundis increased, it is apt to be polarized to be more readily soluble inwater and, if the organic value (OV) of a given compound is increased,the compound is increased in oleophilicity and lowered in solubility inwater, while being more readily soluble in an organic solvent.

Thus, in the EO adduct of a dihydric alcohol, contained in the ink 2, ifthe I/O ratio is less than 1, the compound tends to be lowered inhydrophilicity and separated in the ink 2, with the compound thenforming oil droplets to deteriorate emission stability of the ink suchas by clogging the nozzle 42. If conversely the I/O ratio exceeds 1.37,the EO adduct tends to be lowered in hydorphobicity to produce thetendency for generating fine bubbles in the ink 2, thus again loweringthe emission stability.

In the following Table 1, the inorganic values (IV), the organic values(OV) and the I/O values for the EO adducts of a dihydric alcohol, shownby the above chemical formulas 4 to 16, are shown. It is noted that theI/O values have been calculated on the basis of Table 1.1, page 13 ofthe aforementioned Yoshio Koda: “Systematic Organic QualitativeAnalysis-Fundamentals and Application”. TABLE 1 EO adducts of aInorganic value Organic Value dihydric alcohols (IV) (OV) I/O Compound 4240 230 1.04 Compound 5 360 290 1.24 Compound 6 480 350 1.37 Compound 7240 190 1.26 Compound 8 300 220 1.36 Compound 9 240 200 1.20 Compound 10300 230 1.30 Compound 11 240 240 1.00 Compound 12 480 360 1.33 Compound13 240 220 1.10 Compound 14 420 310 1.35 Compound 15 240 240 1.00Compound 16 480 360 1.33

It will be seen from Table 1 that the I/O value is not less than 1 andnot larger than 1.37 for the EO adducts of a dihydric alcohol, shown bythe above chemical formulas 4 to 16, and, when contained in the ink 2,such adduct suppresses generation of oil droplets or fine bubbles in theink 2, so that it is possible to prevent failure in emission, such asnon-emission or deviation in emission.

As the EO adducts of a dihydric alcohol, having the hydrocarbon groupswith the number of carbon atoms not larger than 9, and having the I/Ovalues ranging between 1 and 1.37, the organic compounds shown by thechemical formulas 4 to 16 are shown. The present invention is, however,not limited to these organic compounds. That is, such EO adducts of adihydric alcohol, having the I/O values ranging between 1 and 1.37 andthe hydrocarbon groups with the number of carbon atoms not larger than9, may be used as a surfactant for the ink 2 with favorable operationand effect comparable with those of the compounds of the chemicalformulas 4 to 16.

In a 25° C. atmosphere, the dynamic surface tension of the ink 2 at 20Hz (

₂₀), that is, the surface tension when air bubbles are generated every50 msec, and that at 1 Hz (

₁), that is, the surface tension when air bubbles are generated everysec, are set to not less than 30 mN/m and to not larger than 38 mN/m,respectively. With the ink 2, having these values of the dynamic surfacetension, the optical density becomes higher, while the boundary bleedingand speckled color mixing in all-over printing may further besuppressed. The reason is that, in conjunction with the above-describedoperation and effect of having contained in the ink 2 the EO adducts ofa dihydric alcohol, having the hydrocarbon groups with the number ofcarbon atoms not larger than 9, and having the I/O values rangingbetween 1 and 1.37, the rate of penetration of the ink 2 into therecording paper sheet P, in other words, the spreading of the ink 2 fromits deposited position along the direction of thickness and along theplanar direction of the recording paper sheet P, along its pulp fibers,becomes uniform.

It is noted that the dynamic surface tension may be measured by e.g. adynamic surface tension meter produced on the basis of the knownprinciple for measuring the dynamic surface tension as disclosed in, forexample the Japanese Laid-Open Patent Publication 63-31237. For example,a dynamic bubble pressure surface tension meter, manufactured by KRUSS,capable of measuring the dynamic surface tension by the maximum bubblepressure method (Trade name: BP-2), or a dynamic surface tensionmeasurement device, manufactured by LAUDA (trade name: MPT2), may beused.

In the ink 2, the dynamic surface tension may basically be adjusted byselecting the sort of the EO adduct of the dihydric alcohol, having ahydrocarbon group with 9 or less carbon atoms and having the I/O ratioranging between 1 and 1.37, or by adjusting the amount of the adduct tobe contained in the ink 2. However, in case it is difficult to adjustthe dynamic surface tension satisfactorily, it is possible to addroutinely used surfactants insofar as such known surfactants are notdeterrent to the operation and effect that may be accrued from the EOadduct of a dihydric alcohol having a hydroxyl group with 9 or lesscarbon atoms and having the value of the I/O value ranging between 1 and1.37. Examples of the routinely used surfactants include special phenolbased nonionic surfactants, such as polycyclic phenol ethoxylates,ester-based nonionic surfactants, such as ethylene oxide adducts ofglyceride, polyethylene glycol oleate, polyoxyalkylene taloate, sorbitanlaurylester, sorbitan oleylester, and polyoxyethylene sorbitaneoleylester, amide-based non-ionic surfactants, such as coconut oil fattyacid diethanol amide, or polyoxyethylene coconut oil fatty aciddiethanol amide and polyoxyethylene coconut oil fatty acid monoethanolamide, acetylene glycol and ethylene oxide adducts thereof, anionicsurfactants, such as alcohol sulfate sodium salts, higher alcoholsulfate sodium salts, polyoxyethylene alkyl phenylether sulfuric acidester ammonium salts, and alkylbenzene sulfonic acid sodium salts,cationic surfactants, such as mono long chain alkyl cation, di longchain alkyl cation or alkylamine oxide, and amphoteric surfactants, suchas laurylamido propyl acetic acid betaine and laurylamino acetic acidbetaine. These known surfactants may be used alone or as a mixture.

The aforementioned known surfactants are added in an amount not largerthan 30 mass wt % and preferably not larger than 20 mass wt %, based onthe total weight of the EO adduct of a dihydric alcohol having ahydrocarbon group with 9 or less carbon atoms and having the I/O ratiovalue ranging between 1 and 1.37, contained in the ink 2. If the knownsurfactants are added in an amount exceeding 30 mass wt % of the totalweight of the EO adduct of a dihydric alcohol, having a hydrocarbongroup with 9 or less carbon atoms and having the I/O ratio value rangingbetween 1 and 1.37, the risk is high that the optical density is loweredand boundary bleeding or speckles in color mixing in all-over printing.

In addition to the aforementioned colorants, solvents, EO adducts of adihydric alcohols, functioning as a surfactant, having hydrocarbongroups with 9 or less carbon atoms and also having the I/O ratio valueranging between 1 and 1.37, and the routinely used surfactants,viscosity adjustment agents, pH adjustment agents, antiseptics,rust-proofing agents or mildew-preventatives, may also be added to theink 2. Specifically, the viscosity adjustment agents and the pHadjustment agents may be exemplified by proteins, such as gelatin andcasein, natural rubber, such as gum Arabic, cellulose derivatives, suchas methyl cellulose, carboxy methyl cellulose or hydroxylmethylcellulose, natural high polymeric materials, such as ligninsulfonates orshellac, polyacrylates, styrene-acrylate copolymer, polyvinyl alcoholand polyvinyl pyrrolidone. These may be used alone or in combination.The antiseptics, rust-proofing agents or mildew-preventatives may beexemplified by benzoic acid, dichlorophene, hexachlophene, sorbic acid,p-hydroxybenzoate and ethylene diamine tetraacetate (EDTA), these beingused either alone or in combination.

The above ink 2 may be prepared by mixing the aforementioned colorant,solvent and the EO adduct of a dihydric alcohol, having a hydrocarbongroup with 9 or less carbon atoms and having the I/O ratio rangingbetween 1 and 1.37, by predetermined proportions, and by agitating anddispersing the resulting mass, such as by a screw, under heating toambient temperature or to a temperature on the order of 40° C. to 80° C.

Referring to FIGS. 2 and 3, the ink 2, prepared as described above, isaccommodated in each ink tank. It is noted that the ink with a yellowcolor is accommodated in the ink tank 11 y, the ink with a magenta coloris accommodated in the ink tank 11 m, the ink with a cyan color isaccommodated in the ink tank 11 c and the ink with a cyan color isaccommodated in the ink tank 11 k.

The head cartridge 3, that may be mounted to and dismounted from themain printer body unit 4, making up the printer apparatus 1, and the inktanks 11 y, 11 m, 11 c and 11 k, will now be explained with reference tothe drawings.

The head cartridge 3 for printing on the recording paper sheet P isloaded from the side of the upper surface of the main printer body unit4, that is, from the direction of an arrow A in FIG. 1, and emits theink 2 onto the recording paper sheet P, fed by the paper sheetsupplying/discharging mechanism 54, in order to emit the ink 2 to effectprinting.

The head cartridge 3 pulverizes the ink 2 into extremely fine particles,by the pressure generated by pressure generating means of, for examplethe electro-thermal transducing type or an electromechanical transducingtype device, to spray the ink as fine droplets onto the major surface ofthe support, such as the recording paper sheet P. Specifically, the headcartridge 3 includes a main cartridge body unit 21, on which are loadedthe ink tanks 11 y, 11 m, 11 c and 11 k, as vessels, each of which ischarged with the ink 2. In the following, the ink tanks 11 y, 11 m, 11 cand 11 k are also simply referred to as an ink tank 11.

The ink tank 11, which may be mounted to and dismounted from the headcartridge 3, includes a tank vessel 12, prepared on injection moldinge.g. a resin material, such as polypropylene, exhibiting strength andresistance against the ink. The tank vessel 12 is formed to asubstantially rectangular shape, having a dimension substantially equalto the width-wise size of the recording paper sheet P, traveling alongits longitudinal direction, for thereby increasing the capacity of theink stored therein.

Specifically, the tank vessel 12, forming the ink tank 11, is providedwith an ink reservoir 13, accommodating the ink 2, an ink supplying unit14 for supplying the ink 2 from the ink reservoir 13 into the maincartridge body unit 21 of the head cartridge 3, a series ofcommunication ports 15 for taking in air from outside into the inkreservoir 13, an air inlet duct 16 for introducing air taken in viacommunication ports 15 into the ink reservoir 13, an ink storage 17 fortransient storage of the ink 2 between the communication ports 15 andthe air inlet duct 16, a retention lug 18 for retaining the ink tank 11by the main cartridge body unit 21 and an engagement step 19.

The ink reservoir 13, formed of a material of high air tightness,delimits a spacing in which to accommodate the ink 2. The ink reservoir13 is formed to a substantially rectangular shape having a long-sidedimension substantially equal to the width-wise size of the recordingpaper sheet P, traveling along its longitudinal direction, that is,along the direction indicated by arrow W in FIG. 3.

The ink supplying unit 14 is provided at a mid part on the lower surfaceof the ink reservoir 13. This ink supplying unit 14 is a substantiallyprotuberantly-shaped nozzle kept in communication with the ink reservoir13. The distal end of the nozzle is fitted to a connecting part 26 ofthe head cartridge 3 as later explained to connect the tank vessel 12 ofthe ink tank 2 with the main cartridge body unit 21 of the headcartridge 3.

Referring to FIGS. 4A and 4B, the ink supplying unit 14 is provided witha supply port 14 b for supplying the ink 2 to a bottom surface 14 a ofthe ink tank 11. On this bottom surface 14 a, there are provided a valve14 c for opening/closing the supply port 14 b, a coil spring 14 d forbiasing the valve 14 c in a direction of closing the supply port 14 b,and an opening/closing pin 14 e for opening/closing the valve 14 c. In astage prior to loading the ink tank 11 to the main cartridge body unit21 of the head cartridge 3, the supply port 14 b, connected to theconnecting part 26 of the head cartridge 3 for supplying the ink 2, isclosed by the valve 14 c being biased in a direction of closing thesupply port 14 b, under the bias of the coil spring 14 d, as a biasingmember, as shown in FIG. 4A. When the ink tank 11 is loaded on the maincartridge body unit 21, the opening/closing pin 14 e is uplifted in adirection opposite to the biasing direction of the coil spring 14 d, byan upper part of the connecting part 26 of the main cartridge body unit21 forming the head cartridge 3, as shown in FIG. 4B. Theopening/closing pin 14 e, thus uplifted, uplifts the valve 14 c, againstthe bias of the coil spring 14 d, for opening the supply port 14 b. Thisconnects the ink supplying unit 14 of the ink tank 11 to the connectingpart 26 of the head cartridge 3, for establishing communication betweenthe ink reservoir 13 and an ink well 31 to enable the ink 2 to besupplied to the ink well 31.

When the ink tank 11 is extracted from the connecting part 26 of thehead cartridge 3, that is, when the ink tank 11 is dismounted from aloading part 22 of the head cartridge 3, the uplifted state of the valve14 c by the opening/closing pin 14 e is canceled, such that the valve 14c is moved in the biasing direction of the coil spring 14 d to close thesupply port 14 b. This prohibits the ink 2 from leaking from the insideof the ink reservoir 13 even in a state in which the distal end of theink supplying unit 14 is directed downwards just before the ink tank 11is loaded on the main cartridge body unit 21. When the ink tank 11 isextracted from the main cartridge body unit 21, the valve 14 cimmediately closes the supply port 14 b, and hence the ink 2 may beprohibited from leaking from the distal end of the ink supplying unit14.

Referring to FIG. 3, the communication port 15 is an air take-in portfor taking in air from outside the ink tank 11 into the ink reservoir13. The communication port 15 is provided at a preset location in theupper surface of the tank vessel 12 facing the outside when the ink tankis loaded on the loading part 22, here at a mid part on the uppersurface of the vessel, so that the communication port faces the outsideto take in outside air even when the ink tank is mounted on the loadingpart 22. The communication port 15 takes in air into the ink tank in anamount corresponding to a decreased amount of the ink 2 in the inkreservoir 13 when the ink tank 11 is loaded on the main cartridge bodyunit 21 and the ink 2 has flown down from the ink reservoir 13 towardsthe main cartridge body unit 21.

The air inlet duct 16 sets up communication between the ink reservoir 13and the communication port 15 to introduce air taken in at thecommunication port 15 into the ink reservoir 13. Thus, even if, when theink tank 11 is loaded on the main cartridge body unit 21, the ink 2 issupplied to the main cartridge body unit 21 of the head cartridge 3,such that the amount of the ink 2 in the ink reservoir 13 is decreasedto decrease the internal pressure, air is introduced via air inlet duct16 into the ink reservoir 13, so that the internal pressure ismaintained in a state of equilibrium to assure proper supply of the ink2 into the main cartridge body unit 21.

The ink storage 17 is provided between the communication port 15 and theair inlet duct 16 for transiently storing the ink 2, so that, when theink 2 has leaked out from the air inlet duct 16 communicating with theink reservoir 13, the ink 2 will not flow outwards precipitously. Thisink storage 17 is lozenge shaped, with the long diagonal line extendingalong the longitudinal direction of the ink reservoir 13. The inlet duct16 is located at an apex point of the ink storage, lying at a lowermostpoint of the ink reservoir 13, that is, at the lower end of the shortdiagonal line of the lozenge shape, such that the ink 2 introduced fromthe ink reservoir 13 will again be restored into the ink reservoir 13.The communication port 15 is provided at the uppermost end of the shortdiagonal line of the lozenge shape such that the ink 2 introduced fromthe ink reservoir 13 will hardly leak to outside through the port 15.

The retention lug 18 is provided on one lateral short side of the inktank 11 and is engaged in an engagement opening 24 a formed in a latchlever 24 of the main cartridge body unit 21 of the head cartridge 3.This retention lug 18 has an upper surface formed as a planar surfaceextending substantially at right angles to the lateral surface of theink reservoir 13, while having a lower surface inclined from the lateralsurface to the upper surface.

The engagement step 19 is provided at an upper part of the ink tank 11on the opposite lateral side with respect to the lateral side carryingthe retention lug 18. The engagement step 19 is made up by an inclinedsurface 19 a, connecting to the upper surface of the tank vessel 12, andby a planar surface 19 b consecutive to the other end of the inclinedsurface 19 a and extending substantially parallel to the upper surfaceof the tank vessel 12. Since the ink tank 11 is provided with theengagement step 19, the lateral surface thereof provided with the planarsurface 19 b is lower by one step than the upper surface of the tankvessel 12. It is by this step that the ink tank is engaged with anengagement part 23 of the main cartridge body unit 21. The engagementstep 19 is provided on the inserting side lateral surface of the inktank when the ink tank is inserted into the loading part 22 of the headcartridge 3. The engagement step is engaged with the engagement part 23of the loading part 22 of the head cartridge 3 so as to act as a fulcrumpoint of rotation when the ink tank 11 is mounted on the loading part22.

The above-described ink tank 11 includes, in addition to the abovecomponent parts, a residual ink quantity detection unit for detectingthe residual quantity of the ink 2 in the ink reservoir 13, and adiscriminating unit for discriminating the ink tanks 11 y, 11 m, 11 cand 11 k.

The head cartridge 3, on which to load the ink tanks 11 y, 11 m, 11 cand 11 k, accommodating the yellow, magenta, cyan and black inks 2,respectively, as described above, will now be explained in detail.

The head cartridge 3 is made up by the aforementioned ink tank 11 andthe main cartridge body unit 21, as shown in FIGS. 2 and 3. The maincartridge body unit 21 includes loading zones 22 y, 22 m, 22 c and 22 k,on which is loaded the ink tank 11. When these loading zones are denotedin their entirety, they are simply referred to below as the loading part22. The main cartridge body unit 21 also includes the engagement part 23and the latch lever 24 for securing the ink tank 11, a biasing member 25for biasing the ink tank 11 in a takeout direction, the connecting part26 connected to the ink supplying unit 14 so as to be supplied with theink 2, an ink emitting head 27 for emitting the ink 2, and a head cap 28for protecting the ink emitting head 27.

The loading part 22, on which to load the ink tank 11, has asubstantially recessed upper surface for use as an inserting/ejectingopening for the ink tank 11. In this recessed upper surface, there arearrayed the four ink tanks 11 in juxtaposition in a directionsubstantially perpendicular to the width of the recording paper sheet P,that is, in a direction along the feed direction of the recording papersheet P. The loading part 22, in which is loaded the ink tank 11, is ofa length elongated along the printing width, as is the ink tank 11. Theink tank 11 is housed and loaded in the main cartridge body unit 21.

The loading part 22 is a zone in which the ink tank 11 is loaded, asshown in FIG. 2. The zones of the loading part, on which are loaded theink tank 11 y for yellow, the ink tank 11 m for magenta, the ink tank 11c for cyan and the ink tank 11 k for black, are labeled 22 y, 22 m, 22 cand 22 k, respectively. The loading zones 22 y, 22 m, 22 c and 22 k areseparated from each other by partitions 22 a. Meanwhile, the ink tank 11k for black is of a larger thickness in order to accommodate a largerquantity of the ink in view of the generally larger consumption of theblack ink, and hence the ink tank 11 k for black is larger in width thanthe remaining ink tanks. Consequently, the loading zone 22 k is broaderin width than the remaining loading zones 22 y, 22 m, 22 c, 22 k inkeeping with the thickness of the ink tank 11 k.

The opening end of the loading part 22, on which is loaded the ink tank11, is provided with the engagement part 23, as shown in FIG. 3. Thisengagement part 23 is provided at a longitudinal end of the loading part22 so as to be engaged with the engagement step 19 of the ink tank 11.The ink tank 11 may be mounted on the loading part 22 by obliquelyinserting the ink tank 11 into the loading part 22, with the engagementstep 19 of the ink tank 11 first. The side of the ink tank 11 notprovided with the engagement step 19 may then be rotated towards theloading part 22, with the location of engagement of the engagement step19 of the ink tank 11 as the fulcrum point of rotation, for loading theink tank on the loading part 22. In this manner, the ink tank 11 mayreadily be mounted on the loading part 22.

The latch lever 24 is formed by bending a spring sheet and is providedon the lateral surface of the loading part 22 opposite to the engagementpart 23, that is, on the opposite longitudinal end of the loading part22. The proximal end of the latch lever 24 is provided as one with thebottom surface of the opposite lateral surface along the longitudinalend of the loading part 22 so that the distal end thereof is resilientlyflexed in a direction towards and away from the aforementioned lateralsurface. The distal end of the latch lever 24 is provided with anengagement opening 24 a. The latch lever 24 is resiliently deflected theinstant the ink tank 11 is mounted on the loading part 22, with theretention lug 18 of the ink tank 11 then engaging with the engagementopening 24 a to prevent the ink tank 11 from becoming detached from theloading part 22 on which has been loaded the ink tank.

The biasing member 25 is a spring sheet provided on the bottom surfacetowards the lateral surface provided with the engagement step 19 of theink tank 11, with the spring sheet being bent for biasing the ink tank11 in the direction of dismounting the ink tank 11. The biasing member25 includes a top formed by bending and may be resiliently deflected ina direction towards and away from the aforementioned bottom surface, inorder to thrust the bottom surface of the ink tank 11 at the top to biasthe ink tank 11 loaded on the loading part 22 in a direction of beingdismounted from the loading part 22. When the retention lug 18 isdisengaged from the engagement opening 24 a of the latch lever 24, thebiasing member 25 ejects the ink tank 11 from the engagement part 23.

On mid parts along the longitudinal direction of the loading zones 22 y,22 m, 22 c and 22 k, there is provided a connecting part 26 the inksupplying units 14 of the ink tanks 11 y, 11 m, 11 c and 11 k areconnected to when the ink tanks 11 y, 11 m, 11 c and 11 k are mounted tothe loading zones 22 y, 22 m, 22 c and 22 k, respectively. Thisconnecting part 26 operates as an ink supply duct for delivery of theink 2 from the ink supplying unit 14 of the ink tank 11 mounted on theloading part 22 to the ink emitting head 27 provided to the bottomsurface of the main cartridge body unit 21.

Specifically, the connecting part 26 includes an ink well 31 for storingthe ink 2 supplied from the ink tank 11, a sealing member 32 for sealingthe ink supplying unit 14 connected to the connecting part 26, a filter33 for removing impurities in the ink 2 and a valving mechanism 34 foropening/closing the supply duct to the ink emitting head 27, as shown inFIG. 5.

The ink well 31 is a spacing connecting to the ink supplying unit 14 andin which the ink 2 is stored. The sealing member 32 is provided on thetop of the ink well 31 and, when the ink supplying unit 14 of the inktank 11 is connected to the ink well 31 of the connecting part 26, thesealing member hermetically seals the boundary between the ink well 31and the ink supplying unit 14 in order to prevent the ink 2 from leakingto outside. The filter 33 removes dust and dirt, eventually mixed intothe ink 2, such as during the mounting and the dismounting of the inktank 11, and is provided downstream of the ink well 31.

Referring to FIGS. 6A and 6B, the valving mechanism 34 includes an inkinlet duct 34 a, the ink 2 is supplied to from the ink well 31, an inkchamber 34 b, the ink 2 flows to from the ink inlet duct 34 a, an inkeffluent duct 34 c, on which the ink 2 flows out from the ink chamber 34b, an opening 34 d provided between the ink inlet duct 34 a and the inkeffluent duct 34 c of the ink chamber 34 b, a valve 34 e foropening/closing the opening 34 d, a biasing member 34 f for biasing thevalve 34 e in the direction of closing the opening 34 d, a negativepressure adjustment screw 34 g for adjusting the biasing force of thebiasing member 34 f, a valve shaft 34 h connected to the valve 34 e anda diaphragm 34 i connected to the valve shaft 34 h.

The ink inlet duct 34 a is a supply duct connecting to the ink reservoir13 for supplying the ink in the ink reservoir 13 in the ink tank 11through the ink well 31 to the ink emitting head 27. The ink inlet duct34 a is provided for extending from the bottom side of the ink well 31to the ink chamber 34 b. The ink chamber 34 b is a substantiallyrectangular spacing, formed as one with the ink inlet duct 34 a, inkeffluent duct 34 c and with the opening 34 d. The ink 2 flows via theink inlet duct 34 a into the ink chamber 34 b to flow out through theopening 34 d and the ink effluent duct 34 c. The ink effluent duct 34 c,supplied with the ink 2 from the ink chamber 34 b through the opening 34d, connects to the ink emitting head 27. The ink effluent duct 34 cextends from the bottom side of the ink chamber 34 b to the ink emittinghead 27.

The valve 34 e closes the opening 34 d to separate the side of the inkinlet duct 34 a and the side of the ink effluent duct 34 c from eachother. The valve 34 e is moved in the up-and-down direction under thebiasing force of the biasing member 34 f, the force of restoration ofthe diaphragm 34 i, connected to the valve shaft 34 h, and under thenegative pressure of the ink 2 on the side of the ink effluent duct 34c. When at the lower end of the valve stroke, the valve 34 e closes theopening 34 d for separating the ink inlet duct 34 a and the side of theink effluent duct 34 c of the ink chamber 34 b from each other forinterrupting the supply of the ink 2 to the ink effluent duct 34 c. Whenlocated at the lower end of the valve stroke, the valve 34 e, againstthe bias of the biasing member 34 f, the valve 34 e does not separatethe ink inlet duct 34 a and the side of the ink effluent duct 34 c ofthe ink chamber 34 b from each other to enable the ink 2 to be suppliedto the ink emitting head 27. Although there is no limitation to the sortof the material of the valve 34 e, it is formed e.g. of an elasticrubber, such as elastomer, in order to assure sufficient closingcharacteristics.

The biasing member 34 f is e.g. a compression coil spring andinterconnects the negative pressure adjustment screw 34 g and the valve34 e between the upper surface of the valve 34 e and the upper surfaceof the ink chamber 34 b to bias the valve 34 e in a direction of closingthe opening 34 d under its force of elasticity. The negative pressureadjustment screw 34 g adjusts the biasing force of the biasing member 34f. By adjusting the negative pressure adjustment screw 34 g, it ispossible to adjust the biasing force of the biasing member 34 f. By sodoing, the negative pressure of the ink 2 for actuating the valve 34 e,configured for opening/closing the opening 34 d, may be adjusted by thenegative pressure adjustment screw 34 g, as will be explained in detailsubsequently.

The valve shaft 34 h has its one end connected to the valve 34 e and itsother end to the diaphragm 34 i for producing concerted movementsthereof. The diaphragm 34 i is a thin sheet of an elastic materialconnected to the opposite side end of the valve shaft 34 h. Thediaphragm 34 i is a thin flexible sheet connected to the valve shaft 34h. This diaphragm 34 i includes a major surface towards the ink effluentduct 34 c of the ink chamber 34 b and the opposite side major surfacecontacting with atmospheric air, and is elastically deflected towardsthe atmospheric air side and towards the ink effluent duct 34 c sideunder the atmospheric pressure and under the negative pressure of theink 2.

In the above-described valving mechanism 34, the valve 34 e is thrustfor closing the opening 34 d of the ink chamber 34 b under the bias ofthe biasing member 34 f and under the biasing force of the diaphragm 34i, as shown in FIG. 6A. When the ink 2 has been emitted from the inkemitting head 27, such that the negative pressure of the ink 2 in theink chamber 34 b towards the ink effluent duct 34 c divided from the inkchamber by the opening 34 d, is increased, the diaphragm 34 i isuplifted by the atmospheric pressure under the negative pressure of theink 2, as shown in FIG. 6B, for uplifting the valve 34 e, along with thevalve shaft 34 h, against the bias of the biasing member 34 f, as shownin FIG. 6B. At this time, the opening 34 d between the ink inlet duct 34a and the ink effluent duct 34 c of the ink chamber 34 b is opened tosupply the ink 2 from the ink inlet duct 34 a towards the ink effluentduct 34 c. When the negative pressure of the ink 2 is decreased, thediaphragm 34 i is restored to its original shape. The biasing force ofthe biasing member 34 f lowers the valve 34 e, along with the valveshaft 34 h, for closing the ink chamber 34 b. Thus, in the valvingmechanism 34, the above-described operation is repeated each time theink 2 is emitted to increase its negative pressure.

Moreover, with the present connecting part 26, the amount of the ink 2in the ink reservoir 13 is decreased when the ink 2 in the ink reservoir13 is supplied to the ink chamber 34 b. At this time, the atmosphericair is introduced into the ink tank 11 from the air inlet duct 16. Theair introduced into the ink tank 11 is forwarded to an upper part of theink tank 11. This restores the state prior to emission of the inkdroplets i from nozzles 42 a, as later explained, to set up a state ofequilibrium. In this state of equilibrium, there is scarcely no ink 2contained in the air inlet duct 16.

The connecting part 26 is of a complicated structure, as describedabove. It is through this complicated structure that the ink 2 istransported. Since the EO adduct of a dihydric alcohol, having ahydrocarbon group with 9 or less carbon atoms and having the I/O ratioranging between 1 and 1.37, is contained in the ink 2, fine bubbles maybe prevented from being produced in the ink 2 due to the opening/closingoperation of the valve 34 e or transportation of the ink 2 through inkducts, such that the ink not admixed with bubbles may be supplied to theink emitting head 27.

The ink emitting head 27 is arranged for extending along the bottomsurface of the main cartridge body unit 21, and a plurality of nozzles42 a, as ink emission ports for emitting ink droplets i, supplied fromthe connecting part 26, are arranged as shown in FIG. 5. Specifically,these nozzles 42 a are arrayed substantially in a line along the widthof the recording paper sheet P, that is, in a direction indicated byarrow W in FIG. 5, from one color to the next.

A head cap 28 is a cover provided for protecting the ink emitting head27, as shown in FIG. 2. The head cap is retreated from the ink emittinghead 27 during the printing operation.

The head cap 28 is provided with a pair of engagement ribs 28 a on bothends along the opening/closing direction indicated by arrow W in FIG. 2,and with a cleaning roll 28 b, extending along the longitudinaldirection, for sucking off excess ink 2 deposited on an ink emittingsurface 27 a of the ink emitting head 27. The engagement ribs 28 a ofthe head cap 28 are engaged in a pair of engagement grooves 27 b, formedin the ink emitting surface 27 a for extending substantially at rightangles to the direction of the arrow W in FIG. 2, so that the head capis moved for opening/closure along the short side of the ink tank 11,that is, in a direction substantially at right angles to the direction Win FIG. 2. With the head cap 28, excess ink 2 may be sucked off duringthe opening/closure operation, by the cleaning roll 28 b being run inrotation in abutting contact with the ink emitting surface 27 a of theink emitting head 27, thereby cleaning the ink emitting surface 27 a ofthe ink emitting head 27. This cleaning roll 28 b is formed of a highlyhygroscopic material, specifically, a sponge, a non-woven cloth or awoven cloth. Except during the printing operation, the head cap 28closes the ink emitting surface 27 a to prevent the ink 2 in the inkemitting head 27 from becoming dried.

The above-described head cartridge 3 includes, in addition to the abovecomponent parts, a residual quantity detection unit for detecting theresidual quantity of the ink 2 in the ink tank 11, and a discriminatingunit for discriminating the presence/absence of the ink 2 when the inksupplying unit 14 is connected to the connecting part 26.

Referring to FIG. 7, the ink emitting head 27 includes a printed circuitboard 41, as a base, a nozzle sheet 42, provided with plural nozzles 42a, a film 43 for separating the printed circuit board 41 from the nozzlesheet 42 for each nozzle 42 a, an ink liquid chamber 44 for pressurizingthe ink 2 supplied via an ink duct 43, a resistance heater 45 forheating the ink 2 supplied to the ink liquid chamber 44, and an ink duct46 for supplying the ink 2 to the ink liquid chamber 44.

The printed circuit board 41 forms a control circuit, formed by a logicIC (integrated circuit) or a driver transistor, on a semiconductorwafer, formed e.g. of silicon, and forms an upper surface of the inkliquid chamber 44.

The nozzle sheet 42 is a sheet material, with a thickness on the orderof 10 to 15 μm, and is provided with the nozzle 42 a, reduced indiameter towards the emitting surface 41, and having a diameter on theink emitting surface 41 of the order of 20 μm. The nozzle sheet isarranged on the opposite side of the printed circuit board 41, with thefilm 43 in-between, for forming the lower surface of the ink liquidchamber 44.

The film 43 is a dry film resist cured on light exposure, for example,and is formed for surrounding each film 42 a except the communicatingarea with the ink duct 43. The film 43 is interposed between the printedcircuit board 41 and the nozzle sheet 42 for forming the lateral surfaceof the ink liquid chamber 44.

The ink liquid chamber 44, surrounded by the printed circuit board 41,nozzle sheet 42 and the film 43, forms a spacing for pressurizing theink 2 supplied from the ink duct 43 from one nozzle 42 a to the next.

The resistance heater 45 is arranged on the printed circuit board 41,facing the ink liquid chamber 44, and is electrically connected to e.g.a control circuit provided to the printed circuit board 41. Theresistance heater 45 is heated under control by e.g. the control circuitto heat the ink 2 within the ink liquid chamber 44.

The ink duct 46 is connected to the ink effluent duct 34 c of theconnecting part 26 and is supplied with the ink 2 from the ink tank 11connected to the connecting part 26 to supply the ink 2 to each inkliquid chamber 44 communicating with the ink duct 46. That is, the inkduct 46 communicates with the connecting part 26. Thus, the ink 2,supplied from the ink tank 11, flows into the ink duct 46 so as to becharged into the ink liquid chamber 44.

The above-described sole ink emitting head 27 is provided with theresistance heater 45, from one ink liquid chamber 44 to the next, andincludes approximately 100 to 5000 ink liquid chambers 44, provided eachwith the resistance heater 45, from one color ink tank 11 to the next.In the ink emitting head 27, the resistance heaters 45 of the ink liquidchambers 44 are selectively heated, under a command from a controller 68of the printer apparatus 1, as later explained, to emit the ink 2 in theink liquid chamber 44, associated with the heated resistance heater 45,from the nozzle 42 a, associated with the ink liquid chambers 44, in thefrom of ink liquid droplets i.

Specifically, with the ink emitting head 27, the control circuit of theprinted circuit board 41 actuates the resistance heater 45, in acontrolled manner, to supply the pulse current for e.g. 1 to 3 μsec tothe selected resistance heater 45. By so doing, the resistance heater 45of the ink emitting head 27 is heated quickly. Then, an air bubble b isgenerated in the ink 2 in the ink liquid chamber 44, contacting with theresistance heater 45, in the ink emitting head 27, as shown in FIG. 8A.In the ink emitting head 27, the air bubble b is expanded to pressurizethe ink 2, with the extruded ink 2 being emitted as the ink liquiddroplet i, as shown in FIG. 8B. After emission of the ink liquid dropleti, the ink 2 is supplied through the ink duct 43 into the ink liquidchamber 44, in the ink emitting head 27, so that the state prior toemission is again reached.

Meanwhile, the above-described ink emitting head 27 is formed by formingthe film 43 on one major surface of the printed circuit board 41, in itsentirety, shaping the film 43 in keeping with the ink liquid chamber 44,and by laminating the nozzle sheet 42 thereon.

With the above-described ink emitting head 27, the number of heatingsites for the ink 2 is increased with the number of the resistanceheaters 45, so that fine bubbles tend to be generated correspondingly.However, since the ink 2 contains the EO adducts of a dihydric alcoholhaving hydrocarbon groups with 9 or less carbon atoms and having the I/Oratio ranging between 1 and 1.37, it is possible to suppress finebubbles from being produced in the ink 2 in the ink liquid chamber 44 toprevent emission troubles exemplified by non-emission or bent emissionof the ink liquid droplet i.

Referring to the drawings, the main printer body unit 4, forming theprinter apparatus 1, on which to mount the head cartridge 3, constructedas described above, will now be explained.

Referring to FIGS. 1 and 9, the main printer body unit 4 includes a headcartridge loading part 51, the head cartridge 3 is mounted to, a headcartridge holding mechanism 52 for holding and securing the headcartridge 3, a head cap opening/closing mechanism 53, a paper sheetsupplying/discharging mechanism 54 for feeding/discharging the recordingpaper sheet P, a paper sheet feed port 55 for supplying the recordingpaper sheet P to the paper sheet supplying/discharging mechanism 54, anda paper sheet discharge port 56 for outputting the recording paper sheetP from the paper sheet supplying/discharging mechanism 54.

The head cartridge loading part 51 is a recess in which to load the headcartridge 3. The head cartridge 3 is loaded so that the ink emittingsurface 27 a of the ink emitting head 27 will be substantially parallelto the paper sheet surface of the recording paper sheet P, in order toeffect printing on the running recording paper sheet P in keeping withthe data. There are occasions where the head cartridge 3 needs to beexchanged due to ink clogging in the ink emitting head 27. Since thehead cartridge 3 is a consumable commodity, even if it does not have tobe exchanged so often as the ink tank 11, the head cartridge 3 isdetachably held by the head cartridge holding mechanism 52 relative tothe head cartridge 3.

The head cartridge holding mechanism 52 is used for detachably holdingthe head cartridge 3 on the head cartridge loading part 51, and isdesigned and constructed for holding and securing the head cartridge 3,with the head cartridge 3 pressuring against the reference surface 4 ain the main printer body unit 4, with a knob 52 a provided to the headcartridge 3 being retained in position by a biasing member, such as aspring, provided in a retention opening 52 b of the main printer bodyunit 4.

The head cap opening/closing mechanism 53 includes a driving unit foropening/closing the head cap 28 of the head cartridge 3. For printing,the head cap 28 is opened for exposing the ink emitting head 27 to therecording paper sheet P and, when the printing is finished, the head cap28 is closed to protect the ink emitting head 27.

The paper sheet supplying/discharging mechanism 54 includes a drivingunit for transporting the recording paper sheet P. Specifically, thepaper sheet supplying/discharging mechanism transports the recordingpaper sheet P, supplied from the paper sheet feed port 55, to the inkemitting head 27 of the head cartridge 3, and transports the recordingpaper sheet P, on which the ink liquid droplets i, supplied from thenozzles 42 a, have been deposited, to effect the printing, to the papersheet discharge port 56, to outside the apparatus. The paper sheet feedport 55 is an opening for supplying the recording paper sheet P to thepaper sheet supplying/discharging mechanism 54, and is able to stockplural recording paper sheets P in stacked up state on e.g. a tray 55 a.The paper sheet discharge port 56 is an opening through which therecording paper sheet P, on which the ink liquid droplets i have beendeposited by way of printing, are discharged.

A control circuit 61, shown in FIG. 10, for controlling the printing bythe printer apparatus, designed and constructed as described above, willnow be explained with reference to the drawings.

The control circuit 61 includes a printer controller 62 for controllingthe driving of the head cap opening/closing mechanism 53 and the papersheet supplying/discharging mechanism 54 of the main printer body unit4, an emission controller 63 for controlling e.g. the current suppliedto the ink emitting head 27, associated with each color of the ink i, analarm unit 64 for indicating the residual quantity of the ink i of eachcolor, an input/output terminal 65 for inputting/outputting signals foran external apparatus, a ROM (Read Only Memory) 66 having recordedthereon e.g. a control program, a RAM (Random Access Memory) 67 fortransiently recording e.g. a read-out control program and reading outthe so recorded control program as necessary, and a controller 68 forcontrolling various components.

The printer controller 62 actuates a driving motor of the head capopening/closing mechanism 53, based on a control signal from thecontrolling 68, in order to control the head cap opening/closingmechanism for opening/controlling the head cap 28. The printercontroller 62 also actuates a driving motor of the paper sheetsupplying/discharging mechanism 54, based on a control signal from thecontrolling 68, in order to control the paper sheetsupplying/discharging mechanism 54 to feed the recording paper sheet Pfrom the paper sheet feed port 55 of the main printer body unit 4 todischarge the printed paper sheet P from the paper sheet discharge port56 after printing.

The emission controller 63 is an electrical circuit including, forexample, a switching element for on/off controlling the electricalconnection to an external power supply supplying the pulse current tothe resistance heater 45, provided to the ink emitting head 27, aresistor for adjusting the value of the pulse current supplied to theresistance heater 45, and a control circuit for controlling the on/offswitching of e.g. switching elements. The emission controller 63 adjuststhe pulse current e.g. supplied to the resistance heater 45 provided tothe ink emitting head 27 to control the ink emitting head 27 adapted foremitting the ink i from the nozzles 42 a.

The alarm unit 64 is a display means, such as LCD (liquid crystaldisplay), and demonstrates the information exemplified by printingconditions, printing states or residual ink quantities. The alarm unit64 may also be a voice outputting means, such as a loudspeaker, in whichcase the information such as the printing conditions, printing states orthe residual ink quantities is output by voice. The alarm unit 64 mayinclude the display means and the voice outputting means in combination.The alarm may be issued by, for example a monitor or a loudspeaker of aninformation processing device 69.

The input/output terminal 65 sends the information, such as the printingconditions, printing states or the residual ink quantities, over aninterface to e.g. the external information processing device 69. Theinput/output terminal 65 is also supplied from e.g. the informationprocessing device 69 with printing data or with control signals foroutputting the information exemplified by the above-mentioned printingconditions, printing states or the residual ink quantities. Theinformation processing device 69 is an information processing deviceexemplified by e.g. a personal computer or a PDA (Personal DigitalAssistant).

The input/output terminal 65, connected to e.g. the informationprocessing device 69, may use e.g. a serial parallel interface or aparallel interface, and is specifically pursuant to standards, such asUSB (Universal Serial Bus), RS (Recommended Standard) 232C or IEEE(Institute of Electrical and Electronic Engineers) 1394. Theinput/output terminal 65 may have data communication, by a wired orwireless route, with the information processing device 69. Among thestandards for wireless communication, there are, for example, theIEEE802.11a, 802.11b and 802.11g.

Between the input/output terminal 65 and the information processingdevice 69, there may be interposed a network, such as the Internet. Theinput/output terminal 65 is connected in this case to a network,exemplified by LAN (Local Area Network), ISDN (Integrated ServicesDigital Network), xDSL (Digital Subscriber Line), FTHP (Fiber to theHome), CATV (Community Antenna TeleVision) or BS (BroadcastingSatellite), and data communication is carried out in association withvarious protocols, such as TCP/IP (Transmission ControlProtocol/Internet Protocol).

The ROM 66 is a memory, such as EP-ROM (Erasable Programmable Read-OnlyMemory), having stored therein a program for various processingoperations carried out by the controller 68. This stored program isloaded by the controller 68 to the RAM 67. The RAM 67 stores the programas read out from the ROM 66 by the controller 68 or various states ofthe printer apparatus 1.

The controller 68 controls various parts based e.g. on printing datasupplied from the input/output terminal 65 and on data of the residualquantity of the ink 2, supplied from the head cartridge 3. Thecontroller 68 reads out a processing program, controlling the variousparts, based e.g. on the input control signal, from the ROM 66, forstorage in the RAM 67, to control or process various parts based on thisprocessing program.

In the above-described control circuit 61, the processing program isstored in the ROM 66. However, the program storage medium is not limitedto the ROM 66, such that a variety of other recording mediums, such asan optical disc, a magnetic disc, an MO disc or an IC card, having theprocessing program recorded thereon, may also be used. In this case, thecontrol circuit 61 is connected to drives for actuating the recordingmediums either directly or through the information processing device 69for reading out the processing program from these recording mediums.

The printing operation by the printer apparatus 1 will now be explainedwith reference to a flowchart shown in FIG. 11. It is noted that thepresent operation is carried out by processing operations by a CPU(central processing unit), not shown, provided in the controller 68,based on a processing program stored in a memory, such as ROM 66.

First, a user issues a command, by acting e.g. on an operating panelprovided on the main printer body unit 4, in order for the printerapparatus 1 to carry out the printing operation. Then, in a step S1, thecontroller 68 verifies whether or not the ink tank 11 of a preset colorhas been loaded on each loading part 22. If the ink tanks 11 of propercolors are mounted on all of the loading zones 22, the controller 68proceeds to a step S2 and, if otherwise, the controller 68 proceeds to astep S4 to inhibit the printing operation.

The controller 68 in the step S2 verifies whether or not the quantity ofthe ink 2 in the ink tank 11 is less than a predetermined quantity, thatis, whether or not the ink tank 11 is in the ink-depleted state. If itis determined that the ink tank 11 is in the ink-depleted state, thealarm unit 64 issues an alarm to that effect and, in the step S4, theprinting operation is inhibited. If conversely the quantity of the ink 2in the ink tank 11 is above the predetermined value, that is, the inktank is charged with the ink, the printing operation is permitted in astep S3.

For carrying out the printing operation, the controller 68 causes thedriving units 53, 54 to be driven in a controlled manner, by the printercontroller 62, to shift the recording paper sheet P to a printingenabling position. Specifically, the controller 68 causes the actuationof the driving motor, forming the head cap opening/closing mechanism 53,to cause movement of the head cap 28 towards the tray 55 a with respectto the head cartridge 3, to expose the nozzles 42 a of the ink emittinghead 27, as shown in FIG. 12. The controller 68 causes the driving ofthe driving motor, forming the paper sheet supplying/dischargingmechanism 54, to cause the feed movement of the recording paper sheet P.Specifically, the controller 68 controls the paper sheetsupplying/discharging mechanism 54 in such a manner that the recordingpaper sheet P is pulled out from the tray 55 a by a paper sheet feedroll 81, the recording paper sheet P, thus pulled out, is transported bypaired separating rolls 82 a, 82 b, rotating in opposite directions, toa direction reversing roll 83 to reverse the transport direction, therecording paper sheet P then is transported to a transport belt 84, andthe recording paper sheet P, thus transported, is held at a presetposition by retention means 85, to determine the position of depositionof the ink 2.

The controller 68 then controls the ink emitting head 27 by the emissioncontroller 63 and causes the ink liquid droplet i to be emitted anddeposited via nozzles 42 a on the recording paper sheet P, transportedto the printing position, to record an image or a letter/characterformed by ink dots.

Since the ink 2 contains an EO adduct of a dihydric alcohol, having ahydrocarbon group with 9 or less carbon atoms and having an I/O ratioranging between 1 and 1.37, it is possible in the ink emitting head 27to suppress fine bubbles from being generated in the ink 2 charged intothe ink liquid chamber 44, in such a manner as to prevent emissiontroubles, such as non-emission or warped emission of the ink liquiddroplet i. Moreover, since the ink liquid droplet i deposited containsthe EO adduct of a dihydric alcohol, having a hydrocarbon group with 9or less carbon atoms and having an I/O ratio ranging between 1 and 1.37,the image or the letter/character is of a high quality with high opticaldensity and suffers from boundary bleeding or generation of speckledmixed colors in all-over printing only to a lesser extent.

When the ink liquid droplet i has been emitted from the nozzles 42 a,the same quantity of the ink 2 as that emitted as the ink liquid dropleti is instantly replenished into the ink liquid chamber 44 from the inkduct 46, so that the original state is restored, as shown in FIG. 6B.When the ink liquid droplet i is emitted from the ink emitting head 27,such that the negative pressure of the ink 2 in the portion of the inkchamber 34 b towards the ink effluent duct 34 c with respect to theopening 34 d is increased, the diaphragm 34 i is uplifted by atmosphericpressure under the negative pressure of the ink 2, along with the valveshaft 34 h, to uplift the valve 34 e, which has so far kept the opening34 d of the ink chamber 34 b closed under the bias of the biasing member34 f and the diaphragm 34 i, against the bias of the biasing member 34f, as shown in FIG. 6A. The opening 34 d between the ink inlet duct 34 aand the ink inlet duct 34 a of the ink chamber 34 b is opened at thistime to supply the ink 2 from the ink inlet duct 34 a side to the inkeffluent duct 34 c side to replenish the ink 2 to the ink duct 46 of theink emitting head 27. The negative pressure of the ink 2 is thendecreased so that the diaphragm 34 i is reset to its original shape bythe restoring force, with the valve 34 e then being lowered, along withthe valve shaft 34 h, such as to close the ink chamber 34 b. Thus, withthe valving mechanism 34, the above-described operation is repeated eachtime the ink liquid droplet i is emitted to raise the negative pressureof the ink 2.

With the ink emitting head 27, since the ink 2 contains the EO adduct ofa dihydric alcohol having hydrocarbon groups with 9 or less carbon atomsand having the I/O ratio ranging between 1 and 1.37, it is possible tosuppress fine bubbles from being produced in the ink 2 in the ink liquidchamber 44, even when the ink 2 is repeatedly supplied as describedabove, that is, when the ink 2 is repeatedly supplied through a flowduct of a complex profile. Thu, the ink 2 free from fine bubbles may bedelivered to the ink emitting head 27 to prevent emission troublesexemplified by non-emission or bent emission of the ink liquid dropleti.

Consequently, the letter/character or an image consistent with printingdata may be printed with superior quality on the recording paper sheet Pbeing fed by the paper sheet supplying/discharging mechanism 54. Therecording paper sheet P, on which printing has been made as describedabove, is then discharged via paper sheet discharge port 56 by the papersheet supplying/discharging mechanism 54.

With the above-described printer apparatus 1, in which the ink 2,containing the EO adduct of a dihydric alcohol, having a hydrocarbongroup with 9 or less carbon atoms and having an I/O ratio rangingbetween 1 and 1.37, as surfactant, is contained in the ink tank 11, withthe ink 2 being emitted as ink liquid droplet i from the nozzles 42 a,it is possible to suppress fine bubbles from being produced in the ink 2to prohibit emission troubles, with the result that the image is freefrom blurring or white spots and hence there may be obtainedhigh-quality printed image or letter/character.

With the present printer apparatus 1, in which the ink containing the EOadduct of a dihydric alcohol, having a hydrocarbon group with 9 or lesscarbon atoms and having an I/O ratio ranging between 1 and 1.37, assurfactant, is deposited on the recording paper sheet P, for printingthereon, it is possible to effect printing of an image of high qualityand high optical density, suppressed in boundary bleeding or speckledcolor mixing in all-over printing.

With the above-described head cartridge 3, the ink tank 11 may bemounted to or dismounted from the main cartridge body unit 21. However,the present invention is not limited to this configuration. That is,since the head cartridge 3 itself is a consumable item and may bemounted to or dismounted from the main printer body unit 4, the ink tank11 may be mounted as one with the main cartridge body unit 21.

In the above-described embodiment, the present invention is directed toa printer apparatus. However, the present invention is not limited tothis configuration and may broadly be applied to other liquid emittingapparatus, such as facsimile machine, copying machine, an emittingapparatus for DNA chips in the liquid (see Japanese laid-Open PatentPublication 2002-34560) or to a liquid emitting apparatus for emitting aliquid containing electrically conductive particles for forming a wiringpattern for an printed circuit board.

In the foregoing, the ink emitting head 27, in which the ink 2 is heatedby the sole resistance heater 45, and the ink so heated is emitted, istaken as an example for explanation. However, the present invention isnot limited to this configuration and may also be applied to a liquidemitting apparatus provided with emitting means having plural pressuregenerating elements each of which delivers discrete values or the energyat different timings to control the liquid emitting direction.

Moreover, in the foregoing, such an electro-thermal conversion system,in which the ink 2 is emitted from the nozzles 42 a as the ink is heatedby the sole resistance heater 45, is used. This is merely illustrativeand such an electromechanical conversion system may also be used inwhich the ink is emitted electromechanically from the nozzle by anelectromechanical conversion element exemplified by a piezoelectricelement.

In addition, in the foregoing, a line-based printer apparatus 1 has beenexplained. The present invention is not limited to this configurationand may also be applied to a serial-based liquid emitting apparatus inwhich the ink head is moved in a direction substantially at right anglesto the traveling direction of the recording paper sheet P.

EXAMPLE

The present invention will now be explained with reference to samples ofan ink actually prepared as a recording liquid embodying the presentinvention.

[Sample 1]

In the sample 1, a magenta-based ink was first prepared. For preparingthe magenta-based ink, 3 mass wt % of C.I. Acid red, as a colorant, 75mass wt % of water, as a solvent, 10 mass wt % of glycerin, as anothersolvent, 5 mass wt % of 1,3-butanediol, as another solvent, 5 mass wt %of neopentyl glycol, as yet another solvent, and 1.5 mass wt % of thecompound shown by the above chemical formula 4, were mixed together andfiltered by a membrane filter, with a pore size of 0.22 μm (trade name:Millex-0.22), to prepare a magenta-based ink.

Then, a cyan-based ink was prepared. For preparing the cyan-based ink,2.5 mass wt % of C.I. Direct Blue, as a colorant, 76 mass wt % of water,as a solvent, 10 mass wt % of glycerin, as another solvent, 5 mass wt %of 1,3-butanediol, as another solvent, 5 mass wt % of neopentyl glycol,as yet another solvent, and 1.5 mass wt % of the compound shown by theabove chemical formula 4, as a surfactant, were mixed together andfiltered by a membrane filter, with a pore size of 0.22 μm (trade name:Millex-0.22), to prepare a cyan-based ink.

Thus, in the sample 1, a magenta-based ink and a cyan-based ink, eachcontaining an EO adduct of a dihydric alcohol, having a hydrocarbongroup with 8 carbon atoms and having an I/O ratio of 1.04, as shown bythe chemical formula 4, as the surfactant, were prepared.

[Sample 2]

With the sample 2, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that the amount ofaddition of the EO adduct of a dihydric alcohol, shown by the chemicalformula 4, as a surfactant, was set to 1 wt %.

[Sample 3]

With the sample 3, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that the amount ofaddition of the EO adduct of a dihydric alcohol, shown by the chemicalformula 4, as a surfactant, was set to 0.5 wt %.

[Sample 4]

With the sample 4, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that an EO adductof a dihydric alcohol, having a hydrocarbon group with 8 carbon atomsand having an I/O ratio of 1.24, as shown by the chemical formula 5, wasused as a surfactant, in place of the organic compound shown by thechemical formula 4.

[Sample 5]

With the sample 5, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that an EO adductof a dihydric alcohol, having a hydrocarbon group with 8 carbon atomsand having an I/O ratio of 1.37, as shown by the chemical formula 6, wasused as a surfactant, in place of the organic compound shown by thechemical formula 4.

[Sample 6]

With the sample 6, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that an EO adductof a dihydric alcohol, having a hydrocarbon group with 6 carbon atomsand having an I/O ratio of 1.26, as shown by the chemical formula 7, wasused as a surfactant, in place of the organic compound shown by thechemical formula 4.

[Sample 7]

With the sample 7, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that an EO adductof a dihydric alcohol, having a hydrocarbon group with 7 carbon atomsand having an I/O ratio of 1.2, as shown by the chemical formula 9, wasused as a surfactant, in place of the organic compound shown by thechemical formula 4.

[Sample 8]

With the sample 8, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that an EO adductof a dihydric alcohol, having a hydrocarbon group with 9 carbon atomsand having an I/O ratio of 1, as shown by the chemical formula 11, wasused as a surfactant, in place of the organic compound shown by thechemical formula 4.

[Sample 9]

With the sample 9, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that an EO adductof a dihydric alcohol, having a hydrocarbon group with 8 carbon atomsand having an I/O ratio of 1.1, as shown by the chemical formula 13, wasused as a surfactant, in place of the organic compound shown by thechemical formula 4.

[Sample 10]

With the sample 10, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that an EO adductof a dihydric alcohol, having a hydrocarbon group with 9 carbon atomsand having an I/O ratio of 1.04, as shown by the chemical formula 15,was used as a surfactant, in place of the organic compound shown by thechemical formula 4.

[Sample 11]

With the sample 11, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that no EO adductof a dihydric alcohol was added.

[Sample 12]

With the sample 12, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that an EO adductof a dihydric alcohol, shown by the chemical formula 17, was used inplace of the organic compound shown by the chemical formula 4.

[Sample 13]

With the sample 13, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that an EO adductof a dihydric alcohol, shown by the chemical formula 18, was used inplace of the organic compound shown by the chemical formula 4.

[Sample 14]

With the sample 12, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that an EO adductof a dihydric alcohol, shown by the chemical formula 19, was used inplace of the organic compound shown by the chemical formula 4.

[Sample 15]

With the sample 15, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that an EO adductof a dihydric alcohol, shown by the chemical formula 20, was used inplace of the organic compound shown by the chemical formula 4.

[Sample 16]

With the sample 16, a magenta-based ink and a cyan-based ink wereprepared in the same way as with the sample 1, except that an EO adductof a dihydric alcohol, shown by the chemical formula 21, was used inplace of the organic compound shown by the chemical formula 4.

The inorganic value (IO), organic value (OV) and I/O, for the EO adductsof a dihydric alcohol, shown in the above chemical formulas 17 to 21,are shown in the following Table 2. TABLE 2 EO adduct of a Inorganicvalue Organic value dihydric alcohol (IV) (OV) I/O Chemical formula 17240 250 0.96 Chemical formula 18 540 380 1.42 Chemical formula 19 540390 1.38 Chemical formula 20 240 160 1.50 Chemical formula 21 720 5501.31

It will be seen from table 2 that the EO adducts of dhhydric alcohol,shown by the chemical formulas 17 to 20, are deviated from the range ofI/O from 1 to 1.37. Thus, if the EO adduct of dhhydric alcohol, shown bythe chemical formula 17, is contained in the ink, the resultant ink islowered in hydrophilicity, with the EO adduct being separated in the inkto stop up the nozzle as oil droplets to deteriorate emission stability.On the other hand, if the EO adducts of dhhydric alcohol of the chemicalformulas 18 to 20, with the I/O exceeding 1.37, are contained in theink, the resultant ink is lowered in hydrophilicity, whilst fine bubblestend to be generated in the ink to deteriorate the emission stability.

For the magenta-based and cyan-based inks of the respective samples,evaluation was made of emission stability, intermittent emissionstability, optical density, boundary bleeding and speckled color mixingin all-over printing.

Meanwhile, emission stability was evaluated as follows: The inks of therespective samples were charged into respective ink tanks and mounted onthe head cartridge. After emitting the inks by the line-based ink jetprinter apparatus, the head cartridge was transiently dismounted fromthe ink jet printer apparatus and was preserved in an atmosphere of thetemperature of 10° C. and the relative humidity of 50% for five days andthen in an atmosphere of the temperature of 40° C. and the relativehumidity of 50% for five days so as to be exposed to an environment ofthe temperature of 20° C. and the relative humidity of 50%. The headcartridge was then mounted again on the line-based ink jet printerapparatus and a preset area of a copy paper sheet manufactured by RICOH(trade name: My Paper) was coated in its entirety, from one color to thenext, by way of a so-called all-over printing. The ink tanks were thendismounted from the head cartridge and visual check was then conductedas to whether or not fine bubbles have not been generated in the inkemission head. The image printed was also visually checked.

The intermittent emission stability was evaluated by the followingmethod. The inks of respective samples were charged in ink tanks whichwere then loaded on the head cartridge. The inks were emitted by aline-based ink jet printer apparatus and the head cartridge wastransiently dismounted from the ink jet printer apparatus. With theemitting surface of the head cartridge exposed to outside, the headcartridge was allowed to stand stationarily for seven minutes at atemperature of 30° C. and an RH of 10%. The head cartridge was thenmounted on the line-based ink jet printer apparatus and all-overprinting was then carried out for each color on copy sheets manufacturedby RICOH (trade name: MyPaper). A visual check was then conducted of theprinted images.

The optical density was measured by the following method. The inks ofthe respective samples were charged in the ink tanks and loaded on thehead cartridge. All-over printing was then carried out for each color oncopy sheets manufactured by RICOH (trade name: MyPaper) and reflectionoptical density was measured by an optical density meter, manufacturedby MACBETH (trade name: TR924).

The boundary bleeding was measured by the following method. The inks ofthe respective samples were charged in the ink tanks and loaded on thehead cartridge. Then, all-over printing was carried out for each coloron copy sheets manufactured by RICOH (trade name: MyPaper), with therespective colors lying adjacent to one another. The bleeding state atthe boundaries of the colors in the printed image was then visuallychecked.

Evaluation of speckled color mixing in all-over printing was evaluatedby the following method. The ink samples were charged in the respectiveink samples and loaded on the head cartridge. All-over printing wascarried out with blue color several times so that the blue color of eachprinting will overlap and the evenness of the blue color density, thatis, the possible presence of irregular color, in the printed image, wasvisually checked.

The emission stability, intermittent emission stability, opticaldensity, boundary bleeding and speckled color mixing in all-overprinting for the respective samples are shown in the following Table 3:TABLE 3 EO adduct of dihydric alcohol Number of Color C atoms of Sort ofIntermittent mixing in hydrocarbon hydrocarbon Emission emission OpticalBoundary allover Sort I/O group group stability stability densitybleeding printing Sanple 1 Chemical 1.04 8 Straight-

1.12

formula 4 chained Sanple 2 Chemical 1.04 8 Straight-

1.21 ⊚ ⊚ formula 4 chained Sanple 3 Chemical 1.04 8 Straight-

1.15

formula 4 chained Sanple 4 Chemical 1.24 8 Straight-

1.15

formula 5 chained Sanple 5 Chemical 1.37 8 Straight-

1.14

formula 6 chained Sanple 6 Chemical 1.26 6 Straight-

1.15

formula 7 chained Sanple 7 Chemical 1.20 7 Branched ⊚

1.23 ⊚ ⊚ formula 9 Sanple 8 Chemical 1 9 Branched ⊚

1.23 ⊚ ⊚ formula 11 Sanple 9 Chemical 1.10 8 Branched ⊚

1.23 ⊚ ⊚ formula 13 Sanple 10 Chemical 1.04 9 Branched ⊚ ⊚ 1.24 ⊚ ⊚formula 15 Sanple 11 — — — — X Δ 1.01 X X Sanple 12 Chemical 0.96 9Straight-

Δ 1.1 Δ

formula 17 chained Sanple 13 Chemical 1.42 8 Straight- X Δ 1.1 Δ Δformula 18 chained Sanple 14 Chemical 1.38 9 Branched

Δ 1.19 Δ

formula 19 Sanple 15 Chemical 1.5 5 Branched X Δ 1.2 Δ Δ formula 20Sanple 16 Chemical 1.31 12 Straight- Δ Δ 1.11 Δ Δ formula 21 chained

As for emission stability in Table 3, a symbol ⊚ indicates that thereare no white spots in the entire image and that no fine bubbles aregenerated in the ink in the ink emission head, a symbol

indicates that the image quality is not of a problem but there is slightwhite spot in the image and a minor quantity of bubbles are generated inthe ink in the ink emission head, a symbol Δ indicates that a minorquantity of bubbles are generated in the ink in the ink emission head,and a symbol x indicates that there is white spot responsible fordegrading the image quality and a large quantity of fine bubbles aregenerated in the ink in the ink emission head. As for intermittentemission stability in Table 3, a symbol

indicates that the image is clear and free of blurring, a symbol

indicates that the image suffers from slight blurring and a symbol Xindicates that the entire image is blurred and the image quality isseverely degraded. As for boundary bleeding in Table 3, a symbol ⊚indicates that there is no bleeding of each color at the boundary, asymbol

indicates that image quality is not of a problem but that there is aminor quantity of bleeding for each color at the boundary, a symbol

indicates that there is bleeding of each color on the boundary degradingthe image quality and a symbol x indicates that that there is bleedingof each color on the entire boundary significantly degrading the imagequality. As for speckled color mixing in all-over printing in Table 3, asymbol ⊚ indicates that an image printed all-over to a blue color iscompletely free from color irregularities, a symbol

indicates that the image quality is not of a problem but the imagesuffers from color irregularities, even though to a lesser extent, and asymbol x indicates that the entire image suffers from colorirregularities such that the image quality is deterioratedsignificantly.

It may be seen from the results of evaluation shown in Table 3 that, ascompared to the sample 11 not containing the EO adduct of a dihydricalcohol, the samples 12 to 15 with the I/O off the range of 1 to 1.37 orto the sample containing an EO adduct of a dihydric alcohol having ahydrocarbon group with 12 carbon atoms, the samples 1 to 10 containingan EO adduct of a dihydric alcohol, having a hydrocarbon group with 9 orless carbon atoms and having an I/O ratio ranging between 1 and 1.37 arenot of a problem in the image quality in the evaluation of emissionstability, intermittent emission stability, boundary bleeding andspeckled color mixing in all-over printing, while being superior inoptical density.

With the samples 1 to 16, not containing an EO adduct of a dihydricalcohol, having a hydrocarbon group with 9 or less carbon atoms andhaving an I/O ratio ranging between 1 and 1.37, it becomes difficult tosuppress fine air bubbles from being generated in the ink emitting head,while emission defects, such as non-emission or warped emission, as wellas white spots or blurring, are produced to deteriorate the imagequality. Moreover, with the samples 1 to 16, not containing an EO adductof a dihydric alcohol, having a hydrocarbon group with 9 or less carbonatoms and having an I/O ratio ranging between 1 and 1.37, it becomesdifficult to raise the optical density of the image or to suppressgeneration of boundary bleeding or speckled color mixing in all-overprinting, such that no image of high image quality can be produced.

With the samples 1 to 10, containing the EO adduct of a dihydricalcohol, having a hydrocarbon group with 9 or less carbon atoms andhaving an I/O ratio ranging between 1 and 1.37 in contradistinction fromthe above samples 11 to 16, fine bubbles can be suppressed from beingproduced in the ink emission head, such that the nozzles may beprevented from being stopped with these fine bubbles to prevent emissiontroubles, with the result that the image printed may be free from whitespots or blurring and of high quality. With the samples 1 to 10,containing the EO adduct of a dihydric alcohol, having a hydrocarbongroup with 9 or less carbon atoms and having an I/O ratio rangingbetween 1 and 1.37, an image printed may be of high image quality, beingsuperior in optical density and suppressed in boundary bleeding or inspeckled color mixing in all-over printing.

It may be seen from above that addition of the EO adduct of a dihydricalcohol, having a hydrocarbon group with 9 or less carbon atoms andhaving an I/O ratio ranging between 1 and 1.37, to the ink beingprepared, is crucial in producing the ink of high quality superior inemission stability, intermittent emission stability and in opticaldensity and which is suppressed in boundary bleeding and in speckledcolor mixing in all-over printing.

It will also be seen from the results of evaluation of Table 3 that,with the samples 7 to 10, the emission stability is improved further.The reason is that the EO adducts of a dihydric alcohol, represented bythe chemical formulas 9, 11, 13 and 15, as used for the samples 7 to 10,contain branched hydrocarbon groups, with the steric chemical structureof the a dihydric alcohol acting for further suppressing the generationof fine bubbles in the ink.

It may be seen from this that use of an EO adduct of a dihydric alcohol,having a branched hydrocarbon group, as an EO adduct of a dihydricalcohol, having a hydrocarbon group with 9 or less carbon atoms andhaving an I/O ratio ranging between 1 and 1.37, is crucial in thepreparation of the ink having superior emission stability.

Measurement was then made of the dynamic surface tension of the inks ofthe respective samples. The measured results of the dynamic surfacetension of the respective ink samples 1 to 16 are shown in Table 4.TABLE 4 Dynamic surface EO adduct of a Sort of tension (mN/m) dihydricalcohol ink

₂₀

₁ Sample 1 Chemical formula 4 Magenta 29.5 28 cyan 29.1 27.3 Sample 2Chemical formula 4 Magenta 34.1 31.1 cyan 34 30.5 Sample 3 Chemicalformula 4 Magenta 38 35.5 cyan 37.9 35 Sample 4 Chemical formula 5Magenta 38.2 36.1 cyan 37.5 35 Sample 5 Chemical formula 6 Magenta 3936.8 cyan 38.6 36.4 Sample 6 Chemical formula 7 Magenta 37.8 34.7 cyan37 34.2 Sample 7 Chemical formula 9 Magenta 36.8 34.5 cyan 36.2 34Sample 8 Chemical formula 11 Magenta 39.5 37.7 cyan 39 37 Sample 9Chemical formula 13 Magenta 40 38.5 cyan 39.2 38 Sample 10 Chemicalformula 15 Magenta 34.3 32 cyan 34 31.7 Sample 11 — Magenta 55.6 55.5cyan 54 53.9 Sample 12 Chemical formula 17 Magenta 30.1 29 cyan 29.228.5 Sample 13 Chemical formula 18 Magenta 42.5 40.3 cyan 41.8 39.2Sample 14 Chemical formula 19 Magenta 40 39 cyan 39.1 38 Sample 15Chemical formula 20 Magenta 53 52.1 cyan 52.4 51.1 Sample 16 Chemicalformula 21 Magenta 49.1 48 cyan 48.1 47

Here, the dynamic surface tension (

₂₀) at 20 Hz and that (

₁) at 1 Hz were measured, under measurement conditions of 25° C.atmosphere and a capillary diameter of 0.215 mm, using a bubble pressuredynamic surface tension meter (BP-2) manufactured by KRUSS.

It will be seen from measured results shown in Table 4 that, withsamples 2 and 10, allowing for printing of further superior printing ofhigher optical density and lower in boundary bleeding and speckled colormixing in all-over printing, the dynamic surface tension (

₂₀) and the dynamic surface tension (

₁) of each of the magenta-based ink and the cyan-based ink are not lessthan 30 mN/m and not higher than 38 mN/m, respectively.

It may be seen from above that setting the dynamic surface tension at 20Hz (

₂₀) of the ink to 30 mN/m or higher and setting the dynamic surfacetension at 1 Hz (

₁) of the ink to 38 mN/m or lower, in preparing the ink, are crucial forpreparing the ink allowing for high quality printing higher in opticaldensity and which is suppressed in boundary bleeding and in speckledcolor mixing in all-over printing.

INDUSTRIAL APPLICABILITY

The recording liquid of the present invention suffers from bubbling to alesser extent and superior in emission stability and, when the recordingliquid is used for multi-color printing an image or a letter/characteron a paper sheet of medium quality, the recording liquid is high inoptical density and free from boundary bleeding or speckled color mixingin all-over printing, and hence the recording liquid of the presentinvention may be used for high-quality printing.

1. A recording liquid deposited on a support in the state of liquiddroplets for recording thereon, comprising a dyestuff; a solvent fordispersing said dyestuff; and an ethylene oxide adduct of a a dihydricalcohol, containing a hydrocarbon group with 9 or less carbon atoms andhaving a ratio I/V of an inorganic value (IO) to an organic value (OV)not less than 1 and not larger than 1.37.
 2. The recording liquidaccording to claim 1 wherein said ethylene oxide adduct of a dihydricalcohol at least includes a branched hydrocarbon group.
 3. The recordingliquid according to claim 1 wherein said ethylene oxide adduct of adihydric alcohol includes at least one or more of organic compoundsrepresented by the chemical formulas 1 to 3:


4. The recording liquid according to claim 1 wherein the dynamic surfacetension (

₂₀) at 20 Hz is not less than 30 mN/m and wherein the dynamic surfacetension (

₁) is not larger than 38 mN/m.
 5. A liquid cartridge mounted to a liquidsupply device for operating as a supply source for said recording liquidfor said liquid supply device, said liquid supply device being providedto a liquid emitting device adapted for emitting the recording liquid,held in a liquid vessel, in the form of liquid droplets, and depositingthe emitted ink on a support, for effecting the recording, wherein saidrecording liquid comprises a dyestuff, a solvent for dispersing saiddyestuff and an ethylene oxide adduct of a dihydric alcohol, containinga hydrocarbon group with 9 or less carbon atoms and having a ratio I/Vof an inorganic value (IO) to an organic value (OV) not less than 1 andnot larger than 1.37.
 6. The liquid cartridge according to claim 5wherein said ethylene oxide adduct of a dihydric alcohol at leastincludes a branched hydrocarbon group.
 7. The liquid cartridge accordingto claim 5 wherein said ethylene oxide adduct of a dihydric alcoholincludes at least one or more of organic compounds represented by thechemical formulas 1 to 3:


8. The recording liquid according to claim 5 wherein the dynamic surfacetension (

₂₀) at 20 Hz is not less than 30 mN/m and wherein the dynamic surfacetension (

₁) is not larger than 38 mN/m.
 9. The liquid cartridge according toclaim 5 wherein said liquid vessel includes a liquid reservoir foraccommodating said recording liquid, a connecting part for connectingthe liquid cartridge to a liquid supply device so that, when the liquidcartridge is connected to the liquid supply device, the recording liquidcontained in said liquid reservoir may be supplied to said liquid supplydevice, a communication port for taking in outside air in an amountcorresponding to a decreased amount of the recording liquid in saidliquid reservoir when the liquid cartridge is mounted on the liquidsupply device and said recording liquid is supplied from said liquidreservoir to said liquid supply device, an air inlet duct forestablishing communication between said liquid reservoir and thecommunication port for introducing air taken in via said communicationport into said liquid reservoir, and a storage arranged between saidcommunication port and the air inlet duct for storing the recordingliquid flowing out from said liquid reservoir.
 10. A liquid emittingdevice comprising emitting means including a liquid chamber for storinga recording liquid, a supply part for supplying said recording liquid tosaid liquid chamber, one or more pressure generating element(s) providedto said liquid chamber for thrusting said recording liquid stored insaid liquid chamber, and an emitting opening for emitting said recordingliquid, thrust by said pressure generating element, onto the majorsurface of a support from said liquid chamber as a liquid droplet; and aliquid cartridge connected to said emitting means for operating as asupply source for said recording liquid; said recording liquidcomprising a dyestuff, a solvent for dispersing said dyestuff and anethylene oxide adduct of a dihydric alcohol, containing a hydrocarbongroup with 9 or less carbon atoms and having a ratio I/V of an inorganicvalue (IO) to an organic value (OV) not less than 1 and not larger than1.37.
 11. The liquid emitting device according to claim 10 wherein saidethylene oxide adduct of a dihydric alcohol, at least includes abranched hydrocarbon group.
 12. The liquid emitting device according toclaim 10 wherein said ethylene oxide adduct of a dihydric alcohol insaid recording liquid includes at least one or more of organic compoundsrepresented by the chemical formulas 1 to 3:


13. The liquid emission device according to claim 10 wherein therecording liquid has a dynamic surface tension (

₂₀) at 20 Hz not less than 30 mN/m and a dynamic surface tension (

₁) at 1 Hz not larger than 38 mN/m.
 14. The liquid emission deviceaccording to claim 10 wherein said emitting openings of said emissionmeans are juxtaposed in a line.
 15. A liquid emitting method employing aliquid emitting device comprising emitting means including a liquidchamber for storing the recording liquid, a supply part for supplyingsaid recording liquid to said liquid chamber, one or more pressuregenerating element(s) provided to said liquid chamber for thrusting saidrecording liquid stored in said liquid chamber, and an emitting openingfor emitting said recording liquid, thrust by said pressure generatingelement, onto the major surface of a support from said liquid chamber asliquid droplets; and a liquid cartridge connected to said emitting meansfor operating as a supply source for said recording liquid; saidrecording liquid comprising a dyestuff, a solvent for dispersing saiddyestuff and an ethylene oxide adduct of a dihydric alcohol, containinga hydrocarbon group with 9 or less carbon atoms and having a ratio I/Vof an inorganic value (IO) to an organic value (OV) not less than 1 andnot larger than 1.37.
 16. The liquid emitting method according to claim15 wherein said ethylene oxide adduct of a dihydric alcohol in saidrecording liquid at least includes a branched hydrocarbon group.
 17. Theliquid emitting method according to claim 15 wherein at least one ormore of organic compounds represented by the chemical formulas 1 to 3:

is used as said ethylene oxide adduct of the dihydric alcohol in saidrecording liquid.
 18. The liquid emission method according to claim 15wherein the recording liquid has a dynamic surface tension (

₂₀) at 20 Hz not less than 30 mN/m and a dynamic surface tension (

₁) at 1 Hz not larger than 38 mN/m.
 19. The liquid emission methodaccording to claim 15 wherein said emitting openings of said emissionmeans are juxtaposed in a line.